US9492877B2 - Drill - Google Patents

Drill Download PDF

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Publication number
US9492877B2
US9492877B2 US14/342,029 US201114342029A US9492877B2 US 9492877 B2 US9492877 B2 US 9492877B2 US 201114342029 A US201114342029 A US 201114342029A US 9492877 B2 US9492877 B2 US 9492877B2
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Prior art keywords
drill
cutting edge
curve
curvature radius
concave curve
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US14/342,029
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US20140219737A1 (en
Inventor
Kazuteru Takai
Kazutoyo Itoh
Hiroyuki Amano
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OSG Corp
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OSG Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B51/00—Tools for drilling machines
    • B23B51/02—Twist drills
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B51/00—Tools for drilling machines
    • B23B51/06—Drills with lubricating or cooling equipment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B2222/00—Materials of tools or workpieces composed of metals, alloys or metal matrices
    • B23B2222/28—Details of hard metal, i.e. cemented carbide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B2251/00—Details of tools for drilling machines
    • B23B2251/04—Angles, e.g. cutting angles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B2251/00—Details of tools for drilling machines
    • B23B2251/08—Side or plan views of cutting edges
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B2251/00—Details of tools for drilling machines
    • B23B2251/12—Cross sectional views of the cutting edges
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B2251/00—Details of tools for drilling machines
    • B23B2251/12—Cross sectional views of the cutting edges
    • B23B2251/125—Rounded cutting edges
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B2251/00—Details of tools for drilling machines
    • B23B2251/14—Configuration of the cutting part, i.e. the main cutting edges
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B2251/00—Details of tools for drilling machines
    • B23B2251/18—Configuration of the drill point
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B2251/00—Details of tools for drilling machines
    • B23B2251/24—Overall form of drilling tools
    • B23B2251/241—Cross sections of the diameter of the drill
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B2251/00—Details of tools for drilling machines
    • B23B2251/40—Flutes, i.e. chip conveying grooves
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T408/00—Cutting by use of rotating axially moving tool
    • Y10T408/89—Tool or Tool with support
    • Y10T408/909—Having peripherally spaced cutting edges
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T408/00—Cutting by use of rotating axially moving tool
    • Y10T408/89—Tool or Tool with support
    • Y10T408/909—Having peripherally spaced cutting edges
    • Y10T408/9095—Having peripherally spaced cutting edges with axially extending relief channel
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T408/00—Cutting by use of rotating axially moving tool
    • Y10T408/89—Tool or Tool with support
    • Y10T408/909—Having peripherally spaced cutting edges
    • Y10T408/9095—Having peripherally spaced cutting edges with axially extending relief channel
    • Y10T408/9097—Spiral channel

Definitions

  • the present invention relates to a drill that is a rotary cutting tool for hole machining through cutting and is particularly related to a technique of forming chips into a curled short shape without a needle-like projection and smoothly discharging the chips to suppress damage of a drill and further improve a tool life.
  • a drill frequently used as a hole tool is disposed with a cutting edge at an axial tip and a chip discharge flute in an axial direction and is rotated around an axial center to perform cutting with the cutting edge at the tip while discharging chips through the chip discharge flute.
  • Drills described in Patent Documents 1 and 2 are examples thereof. These drills have an inner circumferential portion of a cutting edge formed into a concave curve and an outer circumferential portion formed into a convex corner shape to define an obtuse intersection angle with a margin portion on a drill cross section and are considered to achieve curling of chips and an improvement in strength of the outer circumferential portion of the cutting edge and to have drill durability.
  • a drill described in Patent Document 3 has been proposed.
  • This drill has a convexly-curved cutting edge portion formed into a convexly-curved shape convexed in a drill rotation direction on the outer circumferential end side of a cutting edge and has a concavely-curved cutting edge portion formed into a concavely-curved shape concaved in the drill rotation direction on the inner circumferential side of the convexly-curved cutting edge portion, and the convexly-curved cutting edge portion and the concavely-curved cutting edge portion are smoothly continued.
  • an obtuse intersection angle is made between the cutting edge and a margin portion on the outer circumference of a drill main body, increasing the strength to prevent cracking and chipping from occurring, and since the chips cut by the cutting edge are not segmented at the inner/outer circumferences of the cutting edge and the chips are rolled into the inner circumferential side and sufficiently curled by the convexly-curved cutting edge portion, the chips are smoothly discharged and the tool durability is enhanced.
  • the present invention was conceived in view of the situations and it is therefore an object of the present invention to provide a drill that achieves a shape of chips curled without a needle-like projection and accordingly shortened in overall length and that more smoothly discharges the chips to further improve a tool life.
  • the present invention provides a drill comprising: a chip discharge flute opened in a tip surface; and a cutting edge formed at an intersecting portion between an inner wall surface of the chip discharge flute on a side of a drill rotation direction and a tip flank formed on the tip surface, the cutting edge being made up of a concavely-curved cutting edge portion formed on an inner circumferential side and a convexly-curved cutting edge portion formed on an outer circumferential side, wherein a cross section orthogonal to an axial center has a first convex curve corresponding to the convexly-curved cutting edge portion and a first concave curve corresponding to the concavely-curved cutting edge portion intersecting with each other.
  • the drill of the present invention which comprises: the chip discharge flute opened in the tip surface; and the cutting edge formed at the intersecting portion between the inner wall surface of the chip discharge flute on the side of the drill rotation direction and the tip flank formed on the tip surface, the cutting edge being made up of the concavely-curved cutting edge portion formed on the inner circumferential side and the convexly-curved cutting edge portion formed on the outer circumferential side, since the cross section orthogonal to the axial center of the drill has the first convex curve corresponding to the convexly-curved cutting edge portion and the first concave curve corresponding to the concavely-curved cutting edge portion intersecting with each other, chips generated from the cutting edge are curled and formed into a shape having no needle-like projection and accordingly relatively shortened in overall length and are smoothly discharged with enhanced discharge property and, therefore, the tool life of the drill is further improved.
  • the cross section orthogonal to the axial center has a concave amount LF of the first concave curve set to 0.01D to 0.05D (where D is a drill cutting diameter) relative to a reference line connecting an outer circumferential point, at which an outer circumferential surface of the drill intersects with the first convex curve, and a drill center point. Consequently, the chip shape is curled with a relatively shorter overall length and the durability performance is enhanced while a thrust load during cutting is reduced. If the concave amount LF of the first concave curve becomes less than 0.01D, wear of the drill increases and the durability performance deteriorates.
  • the cross section orthogonal to the axial center has a rake chamfer width LW of 0.008D to 0.06D (where D is a drill cutting diameter) that is a distance from an intersection between a straight line orthogonal to the reference line, which passes through an intersection of the first convex curve and the first concave curve, and the reference line, to the outer circumferential point. Consequently, the chip shape is curled with a relatively shorter overall length and the durability performance is enhanced while the thrust load during cutting is reduced.
  • a rake angle is negative that is an angle between the reference line and the first convex curve at the outer circumferential point. Consequently, a corner portion corresponding to the outer circumferential point is enhanced in strength and prevented from cracking, and the durability performance of the drill is enhanced.
  • the drill has a web thickness CD of 0.15D to 0.4D (where D is a drill cutting diameter). Consequently, transverse strength of the drill is enhanced within a range of the achieved chip discharge property and, therefore, the durability performance of the drill is enhanced.
  • the cross section orthogonal to the axial center has an inner wall surface of the chip discharge flute on a side of rotation direction opposite to the drill rotation direction made up of a second concave curve formed on an inner circumferential side and a second convex curve formed on an outer circumferential side adjacently to the second concave curve, and the second convex curve reaches a heel portion.
  • the chip shape is curled with a relatively shorter overall length and the durability performance is enhanced while the thrust load during cutting is reduced, and since the first convex curve and the second convex curve respectively reinforce the corner portion corresponding to the both end portions, i.e., the heel portion and a margin portion, of an opening edge opened in a C-shape or a U-shape in the tip surface of the chip discharge flute, the corner portion and the margin portion is prevented from cracking and the durability of the drill is enhanced.
  • R 1 , R 2 , R 3 , and R 4 are a curvature radius of the first convex curve, a curvature radius of the first concave curve, a curvature radius of the second concave curve, and a curvature radius of the second convex curve, respectively
  • the drill is set to R 1 : 0.02D to 0.4D and R 2 : 0.15D to 0.5D. Consequently, the chip shape is curled with a relatively shorter overall length and the durability performance is enhanced while the thrust load during cutting is reduced.
  • a relationship between the curvature radius of the first concave curve and the curvature radius of the second concave curve is 0.75 ⁇ R 3 /R 2 ⁇ 1.25. Consequently, the chip discharge flute is formed into a cross section shape having a size without clogging of chips within a range in which rigidity of the drill is ensured. If R 3 /R 2 becomes less than 0.75, the cross section area of the chip discharge flute becomes too small and the clogging of chips occurs and causes breakage of the drill.
  • FIG. 1 is a front view of a drill that is an example of the present invention.
  • FIG. 2 is an enlarged view of a tip portion of the drill in the example of FIG. 1 .
  • FIG. 3 is an enlarged view of a tip surface viewed from one end of the drill in the example of FIG. 1 .
  • FIG. 4 is a diagram for explaining a cross section shape of the chip discharge flute in a cross section orthogonal to an axial center C of the drill of FIG. 1 and is a cross-sectional view taken along the line IV-IV in FIG. 1 .
  • FIG. 5 is an enlarged view for specifically explaining a connecting shape between the first convex curve and the first concave curve in the cross section shape of the chip discharge flute of FIG. 4 .
  • FIG. 6 is a chart of types of work materials used in cutting by the drill in the example of FIG. 1 .
  • FIG. 7 is a diagram of a cross section shape of a straight cutting edge drill used in cutting in a cutting test 1 .
  • FIG. 8 is a diagram of a tip surface shape of the straight cutting edge drill used in the cutting in the cutting test 1 .
  • FIG. 9 is a diagram of a cross section shape of a hooked cutting edge drill used in the cutting test 1 .
  • FIG. 10 is a diagram of a tip surface shape of the hooked cutting edge drill used in the cutting test 1 .
  • FIG. 11 is a view of a durability result acquired by the straight cutting edge drill and the hooked cutting edge drill used in the cutting test 1 .
  • FIG. 12 is a photograph of a chip shape generated in cutting by the straight cutting edge drill in the cutting test 1 .
  • FIG. 13 is a photograph of a chip shape generated in cutting by the hooked cutting edge drill in the cutting test 1 .
  • FIG. 14 is a diagram of a cross section shape of a TYPE- 2 drill used in a cutting test 2 .
  • FIG. 15 is a diagram of a tip surface shape of the TYPE- drill used in the cutting test 2 .
  • FIG. 16 is a view of a durability result acquired by a TYPE- 1 drill and the TYPE- 2 drill used in the cutting test 2 .
  • FIG. 17 is a photograph of a chip shape generated in cutting by the TYPE- 1 drill in the cutting test 2 .
  • FIG. 18 is a photograph of a chip shape generated in cutting by the TYPE- 2 drill in the cutting test 2 .
  • FIG. 19 is a chart of cross section shapes of eleven types of drills No. 1 to No. 12 having mutually different shapes as the TYPE- 1 drill used in a cutting test 3 .
  • FIG. 20 is a chart of cutting test results in the cutting test 3 each of the eleven types of the drills No. 1 to No. 12 .
  • FIG. 21 is a diagram for specifically explaining a corner portion crack in the cutting test result.
  • FIG. 22 is a diagram for specifically explaining significant wear in the cutting test result.
  • FIG. 23 is a diagram for specifically explaining breakage of the drill in the cutting test result.
  • FIG. 1 is a diagram of a drill 10 that is an example of the present invention and is a front view from a direction orthogonal to an axial center C.
  • FIG. 2 is an enlarged view of a tip portion disposed with a cutting edge 12 of the drill 10 .
  • FIG. 3 is an enlarged view of a tip surface disposed with the cutting edge 12 of the drill 10 .
  • FIG. 4 is a cross-sectional view of the drill 10 cut along a surface orthogonal to the axial center C.
  • FIG. 5 is an enlarged view of an end edge portion of an inner wall surface of a chip discharge flute 18 on the drill rotation direction side in the cross-sectional view.
  • the drill 10 is a two-flute twist drill and axially integrally includes a shank portion 14 and a flute portion 16 .
  • the drill 10 is made of cemented carbide, and the surfaces of a tip portion disposed with the cutting edges 12 etc., and the flute portion 16 disposed with the chip discharge flutes 18 are coated with a hard film of TiAlN alloy.
  • the flute portion 16 has a pair of the chip discharge flutes 18 twisted clockwise around the axial center C at a predetermined helix angle ⁇ (e.g., about 30 degrees) and margins 20 are disposed along the chip discharge flutes 18 .
  • the pair of the chip discharge flutes 18 is opened in a C-shape in a tapered tip surface of the drill 10 and respective cutting edges 12 are disposed on opening edges of the chip discharge flutes 18 on the side toward the rotation direction of the drill 10 i.e. facing in the rotation direction of the drill 10 .
  • the margin 20 is disposed along a leading edge 26 that is an end edge of a land 24 separated by the chip discharge flutes 18 on the drill rotation direction side.
  • An outer circumferential surface of the drill 10 is made up of an outer circumferential surface of the margin 20 , a second clearance 28 disposed with a constant radial dimension after the margin 20 .
  • An outer diameter of the margin 20 is substantially the same dimension as a drill diameter (outer diameter of the cutting edges 12 ) D at the tip portion of the drill 10 and is gradually reduced to a smaller diameter from the tip portion of the drill 10 toward the shank portion 14 through a predetermined back taper.
  • the cutting edge 12 is made up of a convexly-curved cutting edge portion 12 a formed on the outer circumferential side and a concavely-curved cutting edge portion 12 b formed on the inner circumferential side.
  • the tapered tip surface of the drill 10 is disposed with a second flank 32 and a third flank 34 behind each of the pair of the cutting edges 12 in the rotation direction.
  • the third flank 34 has an oil hole 22 helically disposed to longitudinally pass through the drill 10 in substantially parallel with the chip discharge flutes 18 and opened such that cutting fluid or air can be supplied to a cutting part as needed.
  • An axial center side portion, i.e., a web thickness portion, of the cutting edge 12 is subjected to R-type thinning and an R-shaped axial center side cutting edge portion 12 c smoothly curved on the bottom view of FIG. 3 is disposed to be smoothly connected to the concavely-curved cutting edge portion 12 b.
  • the chip discharge flute 18 is ground by using a plurality of types of fluting grindstones and has an asymmetrical flute cross-sectional shape.
  • the inner wall surface of the chip discharge flute 18 is C-shaped, and the inner wall surface on the drill rotation direction side is made up of a first convex curve CL 1 corresponding to the convexly-curved cutting edge portion 12 a and having a curvature radius R 1 and a first concave curve CL 2 corresponding to the concavely-curved cutting edge portion 12 b and having a curvature radius R 2 intersecting with each other.
  • a first convex curve CL 1 corresponding to the convexly-curved cutting edge portion 12 a and having a curvature radius R 1
  • a first concave curve CL 2 corresponding to the concavely-curved cutting edge portion 12 b and having a curvature radius R 2 intersecting with each other.
  • the inner wall surface of the chip discharge flute 18 on the rear side of the drill rotation direction is made up of a second concave curve CL 3 having a curvature radius R 3 and smoothly connected to the first concave curve CL 2 and a second convex curve CL 4 having a curvature radius R 4 and smoothly connected to the second concave curve CL 3 .
  • the first convex curve CL 1 corresponding to the convexly-curved cutting edge portion 12 a is a convex surface having the curvature radius R 1 projecting in the rotation direction, the strength against crack is increased as compared to the drills of Patent Documents 1 and 2 having a chamfer-like flat surface.
  • the convexly-curved cutting edge portion 12 a on the outer circumferential side and the concavely-curved cutting edge portion 12 b on the inner circumferential side making up the cutting edge 12 have the first convex curve CL 1 and the first concave curve CL 2 corresponding thereto and intersecting with each other, and a slight ridgeline is formed at an intersection A thereof as indicated by a dashed-dotted line of FIG. 2 . Since chips generated from the cutting edge are generated by the concavely-curved cutting edge portion 12 b corresponding to the first concave curve CL 2 and the inner wall surface, the intersection A is desirably positioned closer to the outer circumference as far as possible so as to acquire curled chips with a shorter overall length.
  • the drill 10 of this example has the first convex curve CL 1 corresponding to the convexly-curved cutting edge portion 12 a on the outer circumferential side and the first concave curve CL 2 corresponding to the concavely-curved cutting edge portion 12 b on the inner circumferential side intersected with each other as described above, the intersection A, i.e., a connection point between the first convex curve CL 1 and the first concave curve CL 2 , is preferably positioned closer to the outer circumference as compared to the conventional drill described in Patent Document 3 having the first convex curve CL 1 and the first concave curve CL 2 smoothly connected along a tangential direction.
  • the drill 10 of this example has a concave amount LF of the first concave curve CL 2 set within a range of 0.01D to 0.05D (where D is a drill cutting diameter) relative to a reference line K connecting an outer circumferential point B, at which the outer circumferential surface of the drill 10 intersects with the first convex curve CL 1 , and the axial center C defined as a drill center point. Since the chips are generated by the concavely-curved cutting edge portion 12 b corresponding to the first concave curve CL 2 having the concave amount LF within the range and the inner wall surface and are formed into a preferred curled shape with a relatively shorter overall length, a durability performance of the drill 10 is enhanced and a thrust load during cutting is reduced.
  • the drill 10 of this example has a rake chamfer width LW set within a range of 0.008D to 0.06D (where D is a drill cutting diameter) that is a radial distance from an intersection E between a straight line orthogonal to the reference line K, which passes through the intersection A of the first convex curve CL 1 and the first concave curve CL 2 , and the reference line K, to the outer circumferential point B. Since the radial dimension of the first convex curve CL 1 having the rake chamfer width LW set within the range is preferably made smaller as compared to the conventional drill described in Patent Document 3, the chip shape is curled with a relatively shorter overall length and a needle-like projection is made smaller.
  • the drill 10 of this example has a rake angle ⁇ , i.e., an angle between the reference line K and the first convex curve CL 1 at the outer circumferential point B, set to be negative so that the strength of a corner portion corresponding to the vicinity of the outer circumferential point B is enhanced.
  • the drill 10 of this example has a web thickness CD set to 0.15D to 0.4D (where D is a drill cutting diameter) so that a cross section area of the chip discharge flute 18 is increased as much as possible while transverse strength is ensured.
  • the drill 10 of this example has the inner wall surface of the chip discharge flute 18 toward the rear side of the rotation direction, i.e., the inner wall surface of the chip discharge flute 18 facing in the opposite direction of the rotation direction, made up of the second concave curve CL 3 formed on the inner circumferential side and the second convex curve CL 4 formed on the outer circumferential side adjacently to the second concave curve CL 3 , and the second convex curve CL 4 is set to reach a heel portion of the land 24 .
  • the second convex curve CL 4 reinforces the heel portion of the land 24 .
  • the drill 10 of this example has the curvature radius R 1 of the first convex curve CL 1 , the curvature radius R 2 of the first concave curve CL 2 , the curvature radius R 3 of the second concave curve CL 3 , and the curvature radius R 4 of the second convex curve CL 4 set within ranges of R 1 : 0.02D to 0.4D and R 2 : 0.15D to 0.5D, and a relationship of the curvature radius R 2 of the first concave curve CL 2 and the curvature radius R 3 of the second concave curve CL 3 is set within a range of 0.75 ⁇ R 3 /R 2 ⁇ 1.25.
  • FIG. 6 depicts types of work materials used in cutting by the drill 10 of this example.
  • a double circle of FIG. 6 indicates a material most suitable for the cutting by the drill 10 and a single circle indicates a material suitable for the cutting by the drill 10 .
  • a cutting test 1 performed by the present inventors will be described.
  • the cutting test 1 was performed by using a hooked cutting edge drill corresponding to the drill 10 of the inventive product and a straight cutting edge drill having cutting edges formed straight under the following cutting test conditions.
  • FIG. 11 depicts a durability test result
  • FIG. 12 depicts a chip shape from the straight cutting edge drill
  • FIG. 13 depicts a chip shape from the hooked cutting edge drill.
  • the drill was broken when the number of holes reaches 1720 .
  • the drill was not broken even when the number of holes reaches 2010 .
  • the durability life is at least increased by about 20%. Comparing the chip shape from the straight cutting edge drill depicted in FIG. 12 with the chip shape from the hooked cutting edge drill depicted in FIG.
  • the chip shape from the straight cutting edge drill is less curled and has a needle-like projection, while the chip shape from the hooked cutting edge drill is further curled and has no needle-like projection, resulting in a smaller overall length, and therefore, the chips from the hooked cutting edge drill are considered to achieve relatively higher discharge property.
  • a cutting test 2 performed by the present inventors will be described.
  • the cutting test 2 was performed by using a TYPE- 1 drill having the first convex curve CL 1 and the first concave curve CL 2 intersecting with each other corresponding to the drill 10 of the inventive product and a TYPE- 2 drill having the first convex curve CL 1 and the first concave curve CL 2 smoothly connected to each other corresponding to the drill of Patent Document 3 under the following cutting test conditions.
  • FIG. 16 depicts a durability test result
  • FIG. 17 depicts a chip shape from the TYPE- 1 drill
  • FIG. 18 depicts a chip shape from the TYPE- 2 drill.
  • the cutting edge of the drill cracked when the number of holes reaches 1500.
  • the drill was not broken even when the number of holes reaches 2500.
  • the durability life is at least increased by about 60%. Comparing the chip shape from the TYPE- 1 drill depicted in FIG. 17 with the chip shape from the TYPE- 2 drill depicted in FIG.
  • the chip shape from the TYPE- 1 drill is not provided with a needle-like projection and has a shorter overall length
  • the chip shape from the TYPE- 2 drill is disposed with a needle-like projection and has a relatively longer overall length, and therefore, the chips from the TYPE- 2 drill are estimated to have relatively lower discharge property, which is considered to be the cause of the durability test result.
  • FIG. 20 depicts test results of the drills No. 1 to No. 12 .
  • a circle indicates an excellent result and a triangle indicates a less favorable result as compared to a circle, while a cross mark indicates an unfavorable result.
  • a corner portion crack indicates a cracked state in the part exemplarily illustrated in FIG. 21 ; significant wear indicates a significantly worn state of the part depicted in FIG. 22 ; and breakage indicates a broken state of the drill depicted in FIG. 23 .
  • the drills No. 1 to No. 3 produced excellent results in the chip shape, the thrust load, and the durability performance.
  • chips were acquired in a shape having a shorter overall length without a needle-like projection as depicted in FIG. 17 with good discharge property, and the thrust load for feeding the drills in the axial center C direction was relatively light at the feed rate of 0.15 mm/rev in the cutting test 3 .
  • the durability performance same as the durability result depicted in TYPE- 1 of FIG. 16 was acquired.
  • the drills No. 4 to No. 12 produced less favorable results indicated by triangles or unfavorable results indicated by cross marks in at least one of the chip shape and the thrust load and had one of the drill breakage, the corner portion crack, and the significant wear in terms of durability performance evaluation.
  • the configurations of the drills No. 4 to No. 12 without good durability performance evaluation lead to the following analysis.
  • the breakage of the drill No. 4 and the drill No. 11 due to clogging of chips is considered to be attributable to reduction in discharge property derived from an excessively small cross section area of the chip discharge flutes 18 .
  • the drill No. 4 has a radius ratio R 3 /R 2 set to an excessively small value of 0.7, which makes the curvature radius R 3 relatively smaller than the curvature radius R 2 , and therefore has an excessively small cross section area of the chip discharge flutes 18
  • the drill No. 11 has an excessively large web thickness of 0.42D and therefore has an excessively small cross section area of the chip discharge flutes 18 .
  • the breakage of the drill No. 5 and the drill No. 10 due to tool rigidity shortage is considered to be attributable to an insufficient drill cross section area.
  • the drill No. 5 has the radius ratio R 3 /R 2 set to an excessively large value of 1.3, which makes the curvature radius R 3 relatively larger than the curvature radius R 2 , and therefore has an excessively small cross section area of the chip discharge flutes 18
  • the drill No. 10 has an excessively small web thickness of 0.13D and therefore has an excessively small cross section area of the chip discharge flutes 18 .
  • the corner portion crack of the drills No. 6 to No. 8 and No. 12 is considered to be attributable to the strength or rigidity shortage of the corner portion.
  • the drill No. 6 has the rake chamfer width LW set to an excessively small value of 0.005D and the curvature radius R 1 of the first convex curve CL 1 set to an excessively small value of 0.018D and therefore cannot achieve the strength of the corner portion.
  • the drill No. 7 has the radius ratio R 3 /R 2 set to an excessively large value of 1.53 and the concave amount LF of the curvature radius R 2 from the reference line K toward the rear side of the rotation direction set to an excessively large value of 0.06D and therefore cannot achieve the strength of the corner portion. It is considered that the drill No.
  • the drill No. 12 has the curvature radius R 2 set to an excessively small value of 0.12D and therefore tends to crack in the corner portion. The significant wear of the drill No.
  • the drill No. 9 is considered to be attributable to a lower cutting efficiency increasing a thrust load for maintaining a predetermined feed rate (0.15 mm/rev).
  • the drill No. 9 has the concave amount LF of the curvature radius R 2 from the reference line K toward the rear side of the rotation direction set to a negative value of ⁇ 0.02D, the radius ratio R 3 /R 2 set to an excessively small value of 0.56, which makes the value of the curvature radius R 2 about twice larger than the curvature radius R 3 , the curvature radius R 2 set to a large value of 0.52D, and the rake chamfer width LW set to an excessively large value of 0.09D, the cutting amount is made relatively smaller in the cutting edge 12 with the large curvature radius R 2 on the rotation direction side relative to the reference line K, accordingly increasing the thrust load.
  • the concave amount LF of the first concave curve CL 2 is within a range of 0.01D to 0.05D, that the rake chamfer width LW is within a range of 0.008D to 0.06D, that the web thickness is within a range of 0.15D to 0.4D, that the curvature radius R 1 of the first convex curve CL 1 is within a range of 0.02D to 0.4D, that the curvature radius R 2 of the first concave curve CL 2 is within a range of 0.15D to 0.5D, and that the curvature radius ratio R 3 /R 2 between the first concave curve CL 2 and the second concave curve CL 3 is within a range of 0.75 to 1.25.
  • the cross section orthogonal to the axial center C has the first convex curve CL 1 corresponding to the convexly-curved cutting edge portion 12 a and the first concave curve CL 2 corresponding to the concavely-curved cutting edge portion 12 b intersecting with each other at the intersection A, chips generated from the cutting edge 12 are curled and formed into a shape having no needle-like projection and accordingly relatively shortened in overall length and are smoothly discharged with enhanced discharge property and, therefore, the tool life of the drill 10 is further improved.
  • the chip shape is curled with a relatively shorter overall length and the durability performance is enhanced while the thrust load during cutting is reduced. If the concave amount LF of the first concave curve CL 2 becomes less than 0.01D, the wear of the drill 10 increases and the durability performance deteriorates. If the concave amount LF of the first concave curve CL 2 exceeds 0.05D, the corner portion of the drill cracks.
  • the cross section orthogonal to the axial center C has the rake chamfer width LW of 0.008D to 0.06D (where D is a drill cutting diameter) that is a distance from the intersection E between a straight line orthogonal to the reference line K, which passes through the intersection A of the first convex curve CL 1 and the first concave curve CL 2 , and the reference line K, to the outer circumferential point B, the chip shape is curled with a relatively shorter overall length and the durability performance is enhanced while the thrust load during cutting is reduced. If the rake chamfer width LW becomes less than 0.008D, the corner portion of the drill cracks. If the rake chamfer width LW exceeds 0.06D, the wear of the drill increases and the durability performance deteriorates.
  • D is a drill cutting diameter
  • the corner portion corresponding to the vicinity of the outer circumferential point B is enhanced in strength and prevented from cracking, and the durability performance of the drill 10 is enhanced.
  • the drill 10 of this example has the web thickness CD of 0.15D to 0.4D, the transverse strength of the drill is enhanced within a range of the achieved chip discharge property and, therefore, the durability performance of the drill is enhanced. If the web thickness CD becomes less than 0.15D, the strength is reduced and the drill is broken. If the web thickness CD exceeds 0.4D, the chip discharge flute becomes relatively small and poor discharge of chips generates clogging, which causes the breakage of the drill.
  • the cross section orthogonal to the axial center C has the inner wall surface of the chip discharge flute 18 on the side of rotation direction opposite to the drill rotation direction made up of the second concave curve CL 3 formed on the inner circumferential side and the second convex curve CL 4 formed on the outer circumferential side adjacently to the second concave curve CL 3 , and the second convex curve CL 4 reaches the heel portion, the chip shape is curled with a relatively shorter overall length and the durability performance is enhanced while the thrust load during cutting is reduced, and since the first convex curve and the second convex curve respectively reinforce the corner portion corresponding to the both end portions, i.e., the heel portion and the margin portion, of an opening edge opened in a C-shape or a U-shape in the tip surface of the chip discharge flute 18 , the corner portion and the margin portion is prevented from cracking and the durability of the drill is enhanced.
  • the drill 10 of this example is set to R 1 : 0.02D to 0.4D and R 2 : 0.15D to 0.5D when R 1 is the curvature radius of the first convex curve CL 1 and R 2 is the curvature radius of the first concave curve CL 2 , the chip shape is curled with a relatively shorter overall length and the durability performance is enhanced while the thrust load during cutting is reduced. If R 1 becomes less than 0.02D or exceeds 0.4D, the thrust load is increased. If the curvature radius R 2 becomes less than 0.15D, the corner portion easily cracks and if exceeding 0.5D, the wear becomes significant.
  • the drill 10 of this example has a radius ratio between the curvature radius R 2 of the first concave curve CL 2 and the curvature radius R 3 of the second concave curve CL 3 within a range of 0.75 ⁇ R 3 /R 2 ⁇ 1.25, the chip discharge flute is formed into a cross section shape having a size without clogging of chips within a range in which the rigidity of the drill 10 is ensured. If R 3 /R 2 becomes less than 0.75, the cross section area of the chip discharge flute becomes too small and the clogging of chips occurs and causes the breakage of the drill. If R 3 /R 2 exceeds 1.25, the cross section area of the chip discharge flute becomes larger and the cross section area of the drill main body becomes smaller, causing the breakage of the drill due to rigidity shortage.
  • first convex curve CL 1 and the first concave curve CL 2 intersecting at the intersection A are arcs having the curvature radiuses R 1 and R 2 in the drill 10 of this example, the curves may not necessarily be arcs.
  • the flute portion 16 of the drill 10 of this example is provided with the pair of the chip discharge flutes 18 twisted clockwise around the axial center C at the predetermined helix angle ⁇ (e.g., about 30 degrees), the present invention is applicable to various drills such as a twist drill having the chip discharge flutes 18 twisted anticlockwise around the axial center C, a straight cutting edge drill having the chip discharge flutes 18 parallel to the axial center C, a drills having the one, two, three or more chip discharge flutes 18 , and a double margin drill having one land disposed with two margins.
  • ⁇ e.g., about 30 degrees
  • the drill 10 of this example is disposed with the oil hole 22 longitudinally passing therethrough in the axial center C direction, the oil hole 22 may be disposed as needed depending on quality etc., of a work material.
  • the margin 20 may not necessarily be disposed.
  • the cross section orthogonal to the axial center C of the drill 10 of this example has the inner wall surface of the chip discharge flute 18 toward the side opposite to the rotation direction made up of the second concave curve CL 3 formed on the inner circumferential side and the second convex curve CL 4 formed on the outer circumferential side adjacently to the second concave curve CL 3 , and the second convex curve CL 4 is set to reach the heel portion of the land 24
  • the second convex curve CL 4 is for the purpose of reinforcing the heel portion of the land 24 and therefore may not be curved or may be removed as needed depending on a material.
  • the curvature radius R 3 may be changed within a range not affecting the curling of chips and the discharge of chips.
  • the drill 10 of the example is made of base material that is super hard tool material such as cemented carbide, another tool material such as high-speed steel is also employable. Intermetallic compounds, a diamond film, etc., are employable as a hard film disposed on the base material for enhancing cutting durability.
  • the suitable intermetallic compounds are metals of the groups IIIb, IVa, Va, and VIa of the periodic table of the elements, for example, carbides, nitrides, and carbonitrides of Al, Ti, V, Cr, etc., or mutual solid solutions thereof and, specifically, TiAlN alloy, TiCN alloy, TiCrN alloy, TiN alloy, etc., are preferably used.
  • a hard film of such an intermetallic compound is preferably disposed by a PVD method such as an arc ion plating method and a sputtering method, the hard film may be disposed by another film formation method such as a plasma CVD method.

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JP5816364B2 (ja) * 2012-05-30 2015-11-18 オーエスジー株式会社 ３枚刃ドリル
US9333564B2 (en) 2013-03-15 2016-05-10 Black & Decker Inc. Drill bit
USD737875S1 (en) * 2013-03-15 2015-09-01 Black & Decker Inc. Drill bit
USD734792S1 (en) * 2013-03-15 2015-07-21 Black & Decker Inc. Drill bit
JP2017164836A (ja) * 2016-03-15 2017-09-21 住友電工ハードメタル株式会社 ドリル
CN106077767B (zh) * 2016-07-28 2018-03-30 山东大学 基于Logistic曲线具有S型刀刃的断屑钻头
JP1581012S (ja) * 2016-11-17 2017-07-10
WO2018123937A1 (ja) * 2016-12-26 2018-07-05 京セラ株式会社 ドリル及びそれを用いた切削加工物の製造方法
EP3342513A1 (en) * 2016-12-28 2018-07-04 Sandvik Intellectual Property AB Coolant delivery system for a deep hole drilling apparatus, deep hole drilling apparatus and a method of deep hole drilling
CN110691665B (zh) 2017-05-29 2021-03-16 京瓷株式会社 钻头以及切削加工物的制造方法
WO2019021785A1 (ja) 2017-07-27 2019-01-31 住友電工ハードメタル株式会社 ドリル
CN111587160B (zh) 2017-12-26 2023-04-14 株式会社Moldino 钻头
JP1622531S (ja) * 2018-08-07 2019-01-21
USD987696S1 (en) * 2021-10-14 2023-05-30 Epstein Industrial Supply. Inc. Drill bit

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CN103764325B (zh) 2016-08-17
US20140219737A1 (en) 2014-08-07
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EP2754518B1 (en) 2018-11-07
WO2013035166A1 (ja) 2013-03-14
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JP5762547B2 (ja) 2015-08-12
EP2754518A4 (en) 2015-04-22

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